A vessel element or vessel member is one of the cell types found in xylem, the water conducting tissue of plants. Vessel elements are found in flowering plants but absent from most gymnosperms such as conifers. Vessel elements are the main feature distinguishing the "hardwood" of angiosperms from the "softwood" of conifers. Xylem is the tissue in vascular plants. There are two kinds of cell which are involved in the actual transport: tracheids and vessel elements. Vessel elements are the building blocks of vessels, which constitute the major part of the water transporting system in those plants in which they occur. Vessels form an efficient system for transporting water from the root to the leaves and other parts of the plant. In secondary xylem – the xylem, produced as a stem thickens rather than when it first appears – a vessel element originates from the vascular cambium. A long cell, oriented along the axis of the stem, called a "fusiform initial", divides along its length forming new vessel elements.
The cell wall of a vessel element becomes "lignified", i.e. it develops reinforcing material made of lignin. The side walls of a vessel element have pits: more or less circular regions in contact with neighbouring cells. Tracheids have pits, but only vessel elements have openings at both ends that connect individual vessel elements to form a continuous tubular vessel; these end openings are called perforations or perforation plates. They have a variety of shapes: the most common are the simple perforation and the scalariform perforation. Other types include the reticulate perforation plate. At maturity the protoplast – the living material of the cell – dies and disappears, but the lignified cell walls persist. A vessel element is a dead cell, but one that still has a function, is still being protected by surrounding living cells; the presence of vessels in xylem has been considered to be one of the key innovations that led to the success of the flowering plants. It was once thought that vessel elements were an evolutionary innovation of flowering plants, but their absence from some basal angiosperms and their presence in some members of the Gnetales suggest that this hypothesis must be re-examined.
Cronquist considered the vessels of Gnetum to be convergent with those of angiosperms. Vessel-like cells have been found in the xylem of Equisetum, Pteridium aquilinum and Regnellidium, the enigmatic fossil group Gigantopteridales. In these cases, it is agreed that the vessels evolved independently, it is possible. Tracheid Niklas, Karl J; the Evolutionary Biology of Plants. Chicago and London: The University of Chicago Press. ISBN 0-226-58082-2. Schweingruber, F. H. Anatomie europäischer Hölzer - Anatomy of European woods. Eidgenössische Forschungsanstalt für Wald, Schnee und Landscaft, Birmensdorf. Haupt, Bern und Stuttgart. Timonen, Tuuli. Introduction to Microscopic Wood Identification. Finnish Museum of Natural History, University of Helsinki. Wilson, K.. B.. The Anatomy of Wood: Its Diversity and Variability. London: Stobart & Son Ltd. ISBN 0-85442-033-9
Silene vulgaris, the bladder campion or maidenstears, is a plant species of the genus Silene of the pink family. It is native to Europe, where in some parts it is eaten, but is widespread in North America, where it is a common wildflower in meadows, open woods, fields; the young shoots and the leaves may be used as food in some countries of the Mediterranean region. The tender leaves may be eaten raw in salads; the older leaves are eaten boiled or fried, sauteed with garlic as well as in omelettes. In Crete it is called Agriopapoula and the locals eat its leaves and tender shoots browned in olive oil. In Cyprus it is widely eaten, so much that it has, in recent years, come back into being cultivated and sold in shops in bunches. Two of the common Cypriot names are Tsakrostoukkia and Strouthouthkia. in Italy the leaves of this plant may be used as an ingredient in risotto. It is known as sculpit, stridolo, or by the obsolete scientific name Silene inflata, as well as sciopentin, or grixol in Veneto, nenkuz, or sclopit in Friuli.
In La Mancha region of Spain, where Silene vulgaris leaves are valued as a green vegetable, there were people known as "collejeros" who picked these plants and sold them. Leaves are small and narrow, so it takes many plants to obtain a sizeable amount. In La Mancha the Silene vulgaris leaves, locally known as "collejas", were used to prepare a dish called gazpacho viudo; the ingredients were flatbread known as tortas de gazpacho and a stew prepared with Silene vulgaris leaves. Other dishes prepared with these leaves in Spain include "potaje de garbanzos y collejas", "huevos revueltos con collejas" and "arroz con collejas". List of plants with edible leaves Castilian-Manchego cuisine Guisado de collejas Arroz con collejas
In botany, secondary growth is the growth that results from cell division in the cambia or lateral meristems and that causes the stems and roots to thicken, while primary growth is growth that occurs as a result of cell division at the tips of stems and roots, causing them to elongate, gives rise to primary tissue. Secondary growth occurs in most seed plants, but monocots lack secondary growth. If they do have secondary growth, it differs from the typical pattern of other seed plants; the formation of secondary vascular tissues from the cambium is a characteristic feature of dicotyledons and gymnosperms. In certain monocots, the vascular tissues are increased after the primary growth is completed but the cambium of these plants is of a different nature. In the living Pteridophytes this feature occurs in plants like Isoetes and Botrychium. In many vascular plants, secondary growth is the result of the activity of the two lateral meristems, the cork cambium and vascular cambium. Arising from lateral meristems, secondary growth increases the girth of the plant root or stem, rather than its length.
As long as the lateral meristems continue to produce new cells, the stem or root will continue to grow in diameter. In woody plants, this process produces wood, shapes the plant into a tree with a thickened trunk; because this growth ruptures the epidermis of the stem or roots, plants with secondary growth also develop a cork cambium. The cork cambium gives rise to thickened cork cells to protect the surface of the plant and reduce water loss. If this is kept up over many years, this process may produce a layer of cork. In the case of the cork oak it will yield harvestable cork. Secondary growth occurs in many nonwoody plants, e.g. tomato, potato tuber, carrot taproot and sweet potato tuberous root. A few long-lived leaves have secondary growth. Abnormal secondary growth does not follow the pattern of a single vascular cambium producing xylem to the inside and phloem to the outside as in ancestral lignophytes; some dicots have anomalous secondary growth, e.g. in Bougainvillea a series of cambia arise outside the oldest phloem.
Ancestral monocots lost their secondary growth and their stele has changed in a way it could not be recovered without major changes that are unlikely to occur. Monocots either have no secondary growth, as is the ancestral case, or they have an "anomalous secondary growth" of some type, or, in the case of palms, they enlarge their diameter in what is called a sort of secondary growth or not depending on the definition given to the term. Palm trees increase their trunk diameter due to division and enlargement of parenchyma cells, termed "primary gigantism" because there is no production of secondary xylem and phloem tissues, or sometimes "diffuse secondary growth". In some other monocot stems as in Yucca and Dracena with anomalous secondary growth, a cambium forms, but it produces vascular bundles and parenchyma internally and just parenchyma externally; some monocot stems increase in diameter due to the activity of a primary thickening meristem, derived from the apical meristem. Bark Cambium Root Stem Tylosis Dendrochronology Herbchronology
A perennial plant or perennial is a plant that lives more than two years. Some sources cite perennial plants being plants; the term is used to differentiate a plant from shorter-lived annuals and biennials. The term is widely used to distinguish plants with little or no woody growth from trees and shrubs, which are technically perennials. Perennials small flowering plants, that grow and bloom over the spring and summer, die back every autumn and winter, return in the spring from their rootstock, are known as herbaceous perennials. However, depending on the rigors of local climate, a plant, a perennial in its native habitat, or in a milder garden, may be treated by a gardener as an annual and planted out every year, from seed, from cuttings or from divisions. Tomato vines, for example, live several years in their natural tropical/subtropical habitat but are grown as annuals in temperate regions because they don't survive the winter. There is a class of evergreen, or non-herbaceous, including plants like Bergenia which retain a mantle of leaves throughout the year.
An intermediate class of plants is known as subshrubs, which retain a vestigial woody structure in winter, e.g. Penstemon; the local climate may dictate whether plants are treated as perennials. For instance, many varieties of Fuchsia are shrubs in warm regions, but in colder temperate climates may be cut to the ground every year as a result of winter frosts; the symbol for a perennial plant, based on Species Plantarum by Linnaeus, is, the astronomical symbol for the planet Jupiter. Perennial plants can be short-lived or they can be long-lived, as are some woody plants like trees, they include a wide assortment of plant groups from ferns and liverworts to the diverse flowering plants like orchids and grasses. Plants that flower and fruit only once and die are termed monocarpic or semelparous. However, most perennials are polycarpic. Perennials grow structures that allow them to adapt to living from one year to the next through a form of vegetative reproduction rather than seeding; these structures include bulbs, woody crowns, rhizomes plus others.
They might have specialized stems or crowns that allow them to survive periods of dormancy over cold or dry seasons during the year. Annuals produce seeds to continue the species as a new generation while the growing season is suitable, the seeds survive over the cold or dry period to begin growth when the conditions are again suitable. Many perennials have developed specialized features that allow them to survive extreme climatic and environmental conditions; some have adapted to survive cold temperatures. Those plants tend to invest a lot of resource into their adaptations and do not flower and set seed until after a few years of growth. Many perennials produce large seeds, which can have an advantage, with larger seedlings produced after germination that can better compete with other plants; some annuals produce many more seeds per plant in one season, while some perennials are not under the same pressure to produce large numbers of seeds but can produce seeds over many years. Dividing perennial plants is something that gardeners do around the months of October.
The point of doing the division at this time is to allow 6 weeks for adequate root growth prior to the ground reaching a freezing temperature. Due to the leaves falling from trees, as well as the excessive amount of rain received in most places during the fall weeks, the ground has adequate moisture for rapid growth; each type of plant must be separated differently. However, plants such as Irises have a root system known as a Rhizomes, these root systems should be planted with the bulb of the plant just above ground level, with leaves from the following year showing; the point of dividing perennials is to increase the amount of a single breed of plant in your garden. The more you divide your perennial plants every year, the more vast your garden will grow. In warmer and more favorable climates, perennials grow continuously. In seasonal climates, their growth is limited to the growing season. In some species, perennials retain their foliage all year round. Other plants are deciduous perennials, for example, in temperate regions a perennial plant may grow and bloom during the warm part of the year, with the foliage dying back in the winter.
In many parts of the world, seasonality is expressed as wet and dry periods rather than warm and cold periods, deciduous perennials lose their leaves in the dry season. With their roots protected below ground in the soil layer, perennial plants are notably tolerant of wildfire. Herbaceous perennials are able to tolerate the extremes of cold in temperate and Arctic winters, with less sensitivity than trees or shrubs. Perennial plants can be differentiated from annuals and biennials in that perennials have the ability to remain dormant over long periods of time and continue growth and reproduction; the meristem of perennial plants communicates with the hormones produced due to environmental situations and stage of development to begin and halt the ability to grow or flower. There is a distinction between the ability to grow and actual task of growth. For example, most trees regain the ability to grow in the midst of winter but do not initiate physical growth until the spring and summer months.
The start of dormancy can be seen in perennials pla
The dicotyledons known as dicots, are one of the two groups into which all the flowering plants or angiosperms were divided. The name refers to one of the typical characteristics of the group, namely that the seed has two embryonic leaves or cotyledons. There are around 200,000 species within this group; the other group of flowering plants were called monocotyledons or monocots having one cotyledon. These two groups formed the two divisions of the flowering plants. From the 1990s onwards, molecular phylogenetic research confirmed what had been suspected, namely that dicotyledons are not a group made up of all the descendants of a common ancestor. Rather, a number of lineages, such as the magnoliids and groups now collectively known as the basal angiosperms, diverged earlier than the monocots did; the traditional dicots are thus a paraphyletic group. The largest clade of the dicotyledons are known as the eudicots, they are distinguished from all other flowering plants by the structure of their pollen.
Other dicotyledons and monocotyledons have monosulcate pollen, or forms derived from it, whereas eudicots have tricolpate pollen, or derived forms, the pollen having three or more pores set in furrows called colpi. Aside from cotyledon number, other broad differences have been noted between monocots and dicots, although these have proven to be differences between monocots and eudicots. Many early-diverging dicot groups have "monocot" characteristics such as scattered vascular bundles, trimerous flowers, non-tricolpate pollen. In addition, some monocots have dicot characteristics such as reticulated leaf veins. Traditionally the dicots have been called the Dicotyledones, at any rank. If treated as a class, as in the Cronquist system, they could be called the Magnoliopsida after the type genus Magnolia. In some schemes, the eudicots were treated as a separate class, the Rosopsida, or as several separate classes; the remaining dicots may be kept in a single paraphyletic class, called Magnoliopsida, or further divided.
Some botanists prefer to retain the dicotyledons as a valid class, arguing its practicality and that it makes evolutionary sense. The following lists show the orders in the Angiosperm Phylogeny Group APG IV system traditionally called dicots, together with the older Cronquist system. In the Dahlgren and the Thorne systems, the subclass name Magnoliidae was used for the dicotyledons; this is the case in some of the systems derived from the Cronquist system. For each system, only the superorders are listed; the sequence of each system has been altered to pair corresponding taxa, although circumscription of superorders with the same name is not always the same. The Thorne system as depicted by Reveal is: Calyciflorae World list of dicot species via the Catalogue of Life Tree browser for dicot orders and genera with species counts and estimates via the Catalogue of Life
A forb is an herbaceous flowering plant, not a graminoid. The term is used in biology and in vegetation ecology in relation to grasslands and understory. "Forb" is derived from the Greek φορβή, "pasture" or "fodder". The spelling "phorb" is sometimes used, in older usage this sometimes includes graminids and other plants not regarded as forbs. Forbs are members of a guild – a group of plant species with broadly similar growth form. In certain contexts in ecology, guild membership may be more important than the taxonomic relationships between organisms. In addition to its use in ecology, the term "forb" may be used for subdividing popular guides to wildflowers, distinguishing them from other categories such as grasses, sedges and trees; some examples of forbs are clover, sunflower and milkweed. Dicotyledon Herbaceous plant Overgrazing United States Department of Agriculture Natural Resources Conservation Service link to Growth habits Codes and Definitions
Plant ecology is a subdiscipline of ecology which studies the distribution and abundance of plants, the effects of environmental factors upon the abundance of plants, the interactions among and between plants and other organisms. Examples of these are the distribution of temperate deciduous forests in North America, the effects of drought or flooding upon plant survival, competition among desert plants for water, or effects of herds of grazing animals upon the composition of grasslands. A global overview of the Earth's major vegetation types is provided by O. W. Archibold, he recognizes 11 major vegetation types: tropical forests, tropical savannas, arid regions, Mediterranean ecosystems, temperate forest ecosystems, temperate grasslands, coniferous forests, terrestrial wetlands, freshwater ecosystems and coastal/marine systems. This breadth of topics shows the complexity of plant ecology, since it includes plants from floating single-celled algae up to large canopy forming trees. One feature that defines plants is photosynthesis.
Photosynthesis is the process of a chemical reactions to create glucose and oxgyen, vital for plant life. One of the most important aspects of plant ecology is the role plants have played in creating the oxygenated atmosphere of earth, an event that occurred some 2 billion years ago, it can be dated by the deposition of banded iron formations, distinctive sedimentary rocks with large amounts of iron oxide. At the same time, plants began removing carbon dioxide from the atmosphere, thereby initiating the process of controlling Earth's climate. A long term trend of the Earth has been toward increasing oxygen and decreasing carbon dioxide, many other events in the Earth's history, like the first movement of life onto land, are tied to this sequence of events. One of the early classic books on plant ecology was written by J. E. Weaver and F. E. Clements, it talks broadly about plant communities, the importance of forces like competition and processes like succession. Plant ecology can be divided by levels of organization including plant ecophysiology, plant population ecology, community ecology, ecosystem ecology, landscape ecology and biosphere ecology.
The study of plants and vegetation is complicated by their form. First, most plants are rooted in the soil, which makes it difficult to observe and measure nutrient uptake and species interactions. Second, plants reproduce vegetatively, asexually, in a way that makes it difficult to distinguish individual plants. Indeed, the concept of an individual is doubtful, since a tree may be regarded as a large collection of linked meristems. Hence, plant ecology and animal ecology have different styles of approach to problems that involve processes like reproduction and mutualism; some plant ecologists have placed considerable emphasis upon trying to treat plant populations as if they were animal populations, focusing on population ecology. Many other ecologists believe that while it is useful to draw upon population ecology to solve certain scientific problems, plants demand that ecologists work with multiple perspectives, appropriate to the problem, the scale and the situation. Plant ecology has its origin in the application of plant physiology to the questions raised by plant geographers.
Carl Ludwig Willdenow was one of the first to note that similar climates produced similar types of vegetation when they were located in different parts of the world. Willdenow's student, Alexander von Humboldt, used physiognomy to describe vegetation types and observed that the distribution vegetation types was based on environmental factors. Plant geographers who built upon Humboldt's work included Joakim Frederik Schouw, A. P. de Candolle, August Grisebach and Anton Kerner von Marilaun. Schouw's work, published in 1822, linked plant distributions to environmental factors and established the practice of naming plant associations by adding the suffix -etum to the name of the dominant species. Working from herbarium collections, De Candolle searched for general rules of plant distribution and settled on using temperature as well. Grisebach's two-volume work, Die Vegetation der Erde nach Ihrer Klimatischen Anordnung, published in 1872, saw plant geography reach its "ultimate form" as a descriptive field.
Starting in the 1870s, Swiss botanist Simon Schwendener, together with his students and colleagues, established the link between plant morphology and physiological adaptations, laying the groundwork for the first ecology textbooks, Eugenius Warming's Plantesamfund and Andreas Schimper's 1898 Pflanzengeographie auf Physiologischer Grundlage. Warming incorporated plant morphology, physiology taxonomy and biogeography into plant geography to create the field of plant ecology. Although more morphological than physiological, Schimper's has been considered the beginning of plant physiological ecology. Plant ecology was built around static ideas of plant distribution. Henry Chandler Cowles' studies of plant succession on the Lake Michigan sand dunes and Frederic Clements' 1916 monograph on the subject established it as a key element of plant ecology. Plant ecology developed within the wider discipline of ecology over the twentieth century. Inspired by Warming's Plantesamfund, Arthur Tansley set out to map British plant communities.
In 1904 he teamed up with William Gardner Smith and others involved in vegetation mapping to establish the Central Committee for the Survey and Study of British Vegetation shortened to British Vegetation Committee. In 1913, the British Vegetation Committee organised the British Ecological